Techniques for fiber tip re-imaging in lidar systems

ABSTRACT

A light detection and ranging (LIDAR) system is provided that includes an optical source to generate and transmit an optical beam, an optical fiber to guide the optical beam to a fiber tip from which the optical beam is emitted, and a first scanning mirror rotatable along at least one axis to steer the optical beam to scan a scene, and collect light incident upon objects in the scene. The system further includes a first lens, disposed between the optical fiber and the first scanning mirror, to focus the optical beam emitted from the optical fiber to converge at a location near a center of rotation of the first scanning mirror, the first scanning mirror to reflect the optical beam towards an optic, the optic, disposed between the first scanning mirror and the scene, to collimate or focus the optical beam reflected from the first scanning mirror, and a signal processor to determine a range of one or more of the objects from a return signal reflected from the one or more of the objects.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.17/307,896, filed May 4, 2021, which is a continuation of U.S. patentapplication Ser. No. 16/169,633, filed Oct. 24, 2018, now U.S. Pat. No.11,024,669, issued Jun. 1, 2021, which are hereby incorporated byreference in its entirety.

TECHNOLOGICAL FIELD

The present disclosure relates generally to light detection and ranging(LIDAR) and, in particular, to multiple-wavelength LIDAR that providessimultaneous measurement of range and velocity across two dimensions.

BACKGROUND

Fast-scanning mirrors are the primary components used to illuminate ascene in most LIDAR systems today. As shown in FIG. 1A, one mirrortypically scans fast along the X direction (horizon), while anothermirror scans slow along the Y direction (elevation). Upon targetreflection, the same channel that emitted the light detects the light,typically a single mode fiber. The collected light has an alteredfrequency signature that is used to extract range information.Processing range information combined with angle feedback from thegalvanometer (galvo) motor can form a 3D point cloud.

To increase the frame rate, while maintaining the same number of pointsper frame, the X galvo speed is increased. Scanning the galvos fasterthan 100 Hz at long ranges (>3000 degrees per second) severely degradesthe target signal. This is because during the time the laser signal(frequency sweep) propagates to the distant target and returns to thescanning system, the mirror moves due to its high rotational velocity.As shown in FIG. 1B, this slight angle deviation of the fast scanningmirror causes a misalignment of the target signal at the fiber tip. Forsystems with a small fiber tip core diameter, e.g. the ˜10-um diameterfor typical single mode fiber, such an offset can have significantdegradation of detected signal strength. FIG. 2 shows a plot of fibercoupling efficiency versus scanning mirror's rotational velocity in atypical LIDAR system.

BRIEF SUMMARY

Example implementations of the present disclosure are directed to animproved scanner for a LIDAR system with coherent detection. Exampleimplementations of the present disclosure are based on a type of LIDARthat uses frequency modulation (FM) and coherent detection to overcomethe shortcomings of traditional LIDAR systems and the limitations ofprior FM LIDAR systems. Historically, FM LIDAR systems suffer fromsignificant losses in the beam's return path; thus, such systems, whichare often quite bulky, require a higher beam output power to measuredistances comparable to time-of-flight (TOF) LIDAR systems. Alas, therange is limited by the operating distance for eye-safe output powers.

Example implementations of the present disclosure are configured tosimultaneously measure the range and velocity, using coherent detectionand having the added benefit of immunity to crosstalk from other LIDARsystems. Example implementations minimize optical losses in the beam'sreturn path, thereby increasing the system's measurement range.Additionally, by using nondegenerate laser sources, exampleimplementations can leverage mature wavelength division multiplexing(WDM) techniques often used in integrated silicon photonics, a desiredplatform due to its compactness and relative stability in varyingenvironmental conditions.

As described above, the decenter at the fiber tip upon return of thetarget signal is the primary source of the fiber coupling degradationdescribed above. Example implementations of the present disclosureremove this decenter error by re-imaging the fiber tip onto the fastscanning mirror. In accordance with example implementations, the fibertip is artificially placed at or close to the center of rotation of thescanning mirror, and any rotation about this point is observed as atilt, not a decenter.

Another benefit of example implementations is that the mirror on whichthe fiber tip is re-imaged can be made extremely small andtwo-dimensional (2D) microelectromechanical systems (MEMS) mirrors maybe used. This eliminates the need for a second Y mirror and reduces theoverall size of the system. This configuration would still be followedby a collimating lens.

The present disclosure thus includes, without limitation, the followingexample implementations.

Some example implementations provide a light detection and ranging(LIDAR) system comprising an active optical circuit configured togenerate a laser beam, and detect a return laser beam; an opticalscanning system including at least: an optical fiber configured to guidea laser beam to a fiber tip from which the laser beam is emitted; ascanning mirror rotatable along at least one axis to steer the laserbeam to scan a scene, and collect light incident upon any objects in thescene into a return laser beam that is returned to the fiber tip, theoptical fiber being configured to guide the return laser beam from thefiber tip to the active optical circuit; a re-imaging lens locatedbetween the optical fiber and scanning mirror, and configured to focusthe laser beam emitted from the optical fiber onto the scanning mirrorat or close to a center of rotation of the scanning mirror and therebyre-image the fiber tip at or close to the center of rotation, thescanning mirror being configured to reflect the laser beam as adivergent laser beam; and an optic located between the scanning mirrorand the scene, and configured to collimate or focus the divergent laserbeam from the scanning mirror to produce a collimated or focused laserbeam that is launched toward the scene; and a signal processorconfigured to determine a range of the target from the return laserbeam.

In some example implementations of the LIDAR system of any precedingexample implementation, or any combination of preceding exampleimplementations, the optic of the optical scanning system is acollimator configured to collimate the divergent laser beam from thescanning mirror to produce a collimated laser beam that is launchedtoward the scene.

In some example implementations of the LIDAR system of any precedingexample implementation, or any combination of preceding exampleimplementations, the optic of the optical scanning system is a focuslens configured to focus the divergent laser beam from the scanningmirror to produce a focused laser beam that is launched toward thescene.

In some example implementations of the LIDAR system of any precedingexample implementation, or any combination of preceding exampleimplementations, the scanning mirror of the optical scanning system isrotatable along multiple orthogonal axes to steer the laser beam inmultiple dimensions to scan the scene.

In some example implementations of the LIDAR system of any precedingexample implementation, or any combination of preceding exampleimplementations, the scanning mirror of the optical scanning system is afirst scanning mirror, and the optical scanning system further comprisesa second scanning mirror, the first scanning mirror and the secondscanning mirror being rotatable along orthogonal axes to steer the laserbeam in multiple dimensions to scan the scene, the first scanning mirrorbeing rotatable with a faster angular velocity than the second scanningmirror to scan the scene.

Some example implementations provide an optical scanning systemcomprising an optical fiber configured to guide a laser beam to a fibertip from which the laser beam is emitted; a scanning mirror rotatablealong at least one axis to steer the laser beam to scan a scene, andcollect light incident upon any objects in the scene into a return laserbeam that is returned to the fiber tip, the optical fiber beingconfigured to guide the return laser beam from the fiber tip; are-imaging lens located between the optical fiber and scanning mirror,and configured to focus the laser beam emitted from the optical fiberonto the scanning mirror at or close to a center of rotation of thescanning mirror and thereby re-image the fiber tip at or close to thecenter of rotation, the scanning mirror being configured to reflect thelaser beam as a divergent laser beam; and an optic located between thescanning mirror and the scene, and configured to collimate or focus thedivergent laser beam from the scanning mirror to produce a collimated orfocused laser beam that is launched toward the scene.

In some example implementations of the optical scanning system of anypreceding example implementation, or any combination of precedingexample implementations, the optic is a collimator configured tocollimate the divergent laser beam from the scanning mirror to produce acollimated laser beam that is launched toward the scene.

In some example implementations of the optical scanning system of anypreceding example implementation, or any combination of precedingexample implementations, the optic is a focus lens configured to focusthe divergent laser beam from the scanning mirror to produce a focusedlaser beam that is launched toward the scene.

In some example implementations of the optical scanning system of anypreceding example implementation, or any combination of precedingexample implementations, the scanning mirror is rotatable along multipleorthogonal axes to steer the laser beam in multiple dimensions to scanthe scene.

In some example implementations of the optical scanning system of anypreceding example implementation, or any combination of precedingexample implementations, the optic is a collimator configured tocollimate the divergent laser beam from the scanning mirror to produce acollimated laser beam that is launched toward the scene.

In some example implementations of the optical scanning system of anypreceding example implementation, or any combination of precedingexample implementations, the optic is a focus lens configured to focusthe divergent laser beam from the scanning mirror to produce a focusedlaser beam that is launched toward the scene.

In some example implementations of the optical scanning system of anypreceding example implementation, or any combination of precedingexample implementations, the scanning mirror is a first scanning mirror,and the optical scanning system further comprises a second scanningmirror, the first scanning mirror and the second scanning mirror beingrotatable along orthogonal axes to steer the laser beam in multipledimensions to scan the scene, the first scanning mirror being rotatablewith a faster angular velocity than the second scanning mirror to scanthe scene.

In some example implementations of the optical scanning system of anypreceding example implementation, or any combination of precedingexample implementations, the first scanning mirror is rotatable along anazimuth axis, and the second scanning mirror is rotatable along anelevation axis, to scan the scene.

In some example implementations of the optical scanning system of anypreceding example implementation, or any combination of precedingexample implementations, the optic is located between the first scanningmirror and the second scanning mirror.

In some example implementations of the optical scanning system of anypreceding example implementation, or any combination of precedingexample implementations, the optic is a collimator configured tocollimate the divergent laser beam from the first scanning mirror toproduce a collimated laser beam that is reflected by the second scanningmirror and launched toward the scene.

In some example implementations of the optical scanning system of anypreceding example implementation, or any combination of precedingexample implementations, the optic is a focus lens configured to focusthe divergent laser beam from the first scanning mirror to produce afocused laser beam that is reflected by the second scanning mirror andlaunched toward the scene.

In some example implementations of the optical scanning system of anypreceding example implementation, or any combination of precedingexample implementations, the second scanning mirror is located betweenthe first scanning mirror and the scene, and the optic is locatedbetween the second scanning mirror and the scene, and thereby betweenthe first scanning mirror and the scene.

In some example implementations of the optical scanning system of anypreceding example implementation, or any combination of precedingexample implementations, the optic is a collimator configured tocollimate the divergent laser beam from the second scanning mirror toproduce a collimated laser beam that is launched toward the scene.

In some example implementations of the optical scanning system of anypreceding example implementation, or any combination of precedingexample implementations, the optic is a focus lens configured to focusthe divergent laser beam from the second scanning mirror to produce afocused laser beam that is reflected launched toward the scene.

In some example implementations of the optical scanning system of anypreceding example implementation, or any combination of precedingexample implementations, the laser beam is multiple laser beams, and theoptical fiber is an array of optical fibers configured to guide themultiple laser beams to fiber tips from which the multiple laser beamsare emitted.

These and other features, aspects, and advantages of the presentdisclosure will be apparent from a reading of the following detaileddescription together with the accompanying figures, which are brieflydescribed below. The present disclosure includes any combination of two,three, four or more features or elements set forth in this disclosure,regardless of whether such features or elements are expressly combinedor otherwise recited in a specific example implementation describedherein. This disclosure is intended to be read holistically such thatany separable features or elements of the disclosure, in any of itsaspects and example implementations, should be viewed as combinableunless the context of the disclosure clearly dictates otherwise.

It will therefore be appreciated that this Brief Summary is providedmerely for purposes of summarizing some example implementations so as toprovide a basic understanding of some aspects of the disclosure.Accordingly, it will be appreciated that the above described exampleimplementations are merely examples and should not be construed tonarrow the scope or spirit of the disclosure in any way. Other exampleimplementations, aspects and advantages will become apparent from thefollowing detailed description taken in conjunction with theaccompanying figures which illustrate, by way of example, the principlesof some described example implementations.

BRIEF DESCRIPTION OF THE FIGURE(S)

Having thus described example implementations of the disclosure ingeneral terms, reference will now be made to the accompanying figures,which are not necessarily drawn to scale, and wherein:

FIGS. 1A and 1B illustrate an optical scanning system of a typical lightdetection and ranging (LIDAR) system to steer a laser beam to scan ascene, and illustrating decentering of the return laser beam at thefiber tip;

FIG. 2 is a plot of fiber coupling efficiency versus rotational scanningmirror velocity in a typical LIDAR system;

FIG. 3 illustrates a LIDAR system according to example implementationsof the present disclosure;

FIG. 4 is a plot of fiber coupling efficiency versus rotational scanningmirror velocity in the LIDAR system of FIG. 3, according to some exampleimplementations;

FIGS. 5, 6, 7, 8, 9 and 10 illustrate aspects of the optical scanningsystem of the LIDAR system of FIG. 3, according to various exampleimplementations; and

FIG. 11 illustrates the LIDAR system of FIG. 3 configured with multiplebeams, according to some example implementations.

DETAILED DESCRIPTION

Some implementations of the present disclosure will now be describedmore fully hereinafter with reference to the accompanying figures, inwhich some, but not all implementations of the disclosure are shown.Indeed, various implementations of the disclosure may be embodied inmany different forms and should not be construed as limited to theimplementations set forth herein; rather, these example implementationsare provided so that this disclosure will be thorough and complete, andwill fully convey the scope of the disclosure to those skilled in theart. For example, reference may be made herein to quantitative measures,values, relationships or the like (e.g., planar, coplanar,perpendicular). Unless otherwise stated, any one or more if not all ofthese may be absolute or approximate to account for acceptablevariations that may occur, such as those due to engineering tolerancesor the like. Like reference numerals refer to like elements throughout.

Example implementations of the present disclosure are directed to animproved LIDAR system. The LIDAR system may be implemented in anysensing environment, such as, but not limited to, transportation,manufacturing, metrology, medical, and security systems. For example, inthe automotive industry, such a device can assist with spatial awarenessfor automated driver assist systems, or self-driving vehicles.Additionally, it can help with velocity calibration of a moving vehiclewithout the need for a separate inertial movement unit (IMU). In otherexamples, the LIDAR system may provide data that can be used foranalysis of defects, diagnostics, image processing, or otherapplications.

FIG. 3 illustrates a LIDAR system 300 according to exampleimplementations of the present disclosure. The LIDAR system includes oneor more of each of a number of components. A number of examplecomponents are illustrated and described herein. It should be understoodthat in various implementations, the LIDAR system may omit one or moreof the components, or include additional or alternative components thanthose illustrated and described herein. As shown, the LIDAR systemincludes an active optical circuit 302 configured to generate, amplifyand detect optical signals and the like. In some examples, the activeoptical circuit includes lasers at different wavelengths, an opticalamplifier, and photodetectors.

The LIDAR system 300 includes a passive optical circuit 304 with one ormore waveguides to route and manipulate optical signals to appropriateinput/output ports of the active optical circuit 302. The passiveoptical circuit may include one or more optical components such as taps,wavelength division multiplexers (WDMs), splitters/combiners, polarizingbeam splitters (PBSs), Mach-Zehnder interferometers, modulators, opticalattenuators, circulators, collimators and the like.

An optical scanning system 306 includes one or more scanning mirrorsthat are rotatable by galvanometers (galvos) along respective orthogonalaxes to steer optical signals to scan a scene according to a scanningpattern. The optical scanning system also collects light incident uponany objects in the scene into a return laser beam that is returned tothe passive optical circuit 304. In addition to the mirrors and galvos,the optical scanning system may include components such as waveplates,lenses, spectral filters, anti-reflective (AR)-coated windows and thelike.

To control and support the active optical circuit 302, passive opticalcircuit 304 and optical scanning system 306, the LIDAR system 300includes a LIDAR digital signal processor (DSP) 308 configured tofunction as the central processing unit for the system. The LIDAR DSP isconfigured to output digital control signals for a laser driver 310configured to modulate the lasers to provide an optical signal. Adigital-to-analog converter (DAC) 312 may provide signals to the laserdriver.

The LIDAR DSP 308 is configured to output digital control signals forthe optical scanning system 306. A motion control software subsystem 314may control the galvos of the optical scanning system. A DAC 316 mayconvert coordinate routing information from the LIDAR DSP to signalsinterpretable by the galvos. An analog-to-digital converter (ADC) 318may in turn convert information about the galvos' position to a signalinterpretable by the LIDAR DSP.

The LIDAR DSP 308 is further configured to analyze incoming digitalsignals. In some examples, target receivers 320 measure the opticalsignal that carries information about the range of a target. In otherexamples, the target receivers measure the optical signal that carriesinformation about the range and velocity of a target in the form of abeat frequency, modulated optical signal. In some examples, the LIDARDSP is configured to determine or otherwise produce multiplemeasurements of range, or range and velocity, of the target or the sceneincluding the target from multiple signals or a periodic signal, andproduce a multi-dimensional (e.g., 3D, 4D) representation of thescene—such as a multi-dimensional point cloud—from the measurements. AnADC 322 converts signals from the target receivers to signalsinterpretable by the LIDAR DSP.

In some applications, the LIDAR system 300 may additionally include acamera 324 configured to capture images of the scene, and asatellite-based navigation receiver 326 configured to provide ageographic location of the system. A computer vision processor 328 isconfigured to receive the images and geographic location, and send theimages and location or information related thereto to the LIDAR DSP 308.

In operation according to some examples, the LIDAR system 300 isconfigured to use nondegenerate laser sources to simultaneously measurerange and velocity across two dimensions. This capability allows forreal-time, long range 4D measurements (range, velocity, azimuth, andelevation) of the surrounding environment (a scene). The system pointsmultiple modulated laser beams to the same target.

In some examples, the scanning process begins with the laser driver 310and LIDAR DSP 308. The LIDAR DSP instructs the laser driver toindependently modulate the lasers, and these modulated signals propagatethrough the passive optical circuit 304 to the collimator. Thecollimator directs the light to the optical scanning system 306 thatscans the environment over a preprogrammed pattern defined by the motioncontrol software subsystem 314.

The collected optical signals pass through the optical circuits 304, 302to the target receivers 320. In some examples, the LIDAR system 300includes two target receivers per beam. The target receivers measure theoptical signals encoded with range and velocity information about theenvironment. Each beam signal that returns from the target produces atime-shifted waveform. The temporal phase difference between the twowaveforms generates a beat frequency measured on the photodetectors inthe active optical circuit 302.

The analog signals from the target receivers 320 are converted todigital signals using ADC 322. The digital signals are then sent to theLIDAR DSP 308. The LIDAR DSP 308 also receives position data from themotion control software subsystem 314 and galvos as well as image datafrom the computer vision processor 328.

The computer vision processor 328 collects two-dimensional (2D) imagesfrom the camera 324 and sends the data to the LIDAR DSP 308. The systemsoftware then overlays the multi-dimensional representation (e.g., 4Dpoint cloud) with the image data to determine velocity and distance ofobjects in the surrounding area. The system also processes thesatellite-based navigation location data to provide a precise globallocation.

As explained in the Background and Brief Summary section, traditionalLIDAR systems suffer from degraded target signals when the scanningmirrors are rotated with an increased rotational speed. During the timeit takes a laser signal (frequency sweep) to reach the target and returnto the scanning system, the mirror has moved due to its rotationalvelocity, and this slight angle deviation of the fast scanning mirrorcauses misalignment of the target signal at the fiber tip. Exampleimplementations of the present disclosure remove this decenter error byre-imaging the fiber tip onto one of the scanning mirrors, such as thefast scanning mirror. In accordance with example implementations, thefiber tip is artificially placed at or close to the center of rotationof the scanning mirror, and any rotation about this point is observed asa tilt, not a decenter. FIG. 4 shows a plot of fiber coupling efficiencyversus rotational scanning mirror velocity in the LIDAR system of FIG.3, according to some example implementations of the present disclosure.

FIG. 5 illustrates an optical scanning system 500 that may correspond tothe optical scanning system 306 of the LIDAR system 300 of FIG. 3,according to some example implementations. As shown, an optical fiber502 is configured to guide a laser beam to a fiber tip 504 from whichthe laser beam is emitted. The optical scanning system includes a pairof mirrors 506, 508—later identified as first scanning mirror and secondscanning mirror—that rotate along orthogonal axes to steer the laserbeam across a scene 510 according to a scanning pattern. The same systemcollects light reflected by all objects in the scene into the fiber tip.The optical fiber guides the return laser beam from the fiber tip to aphotodetector (e.g., in the active optical circuit 302) that isconfigured to detect the return signal.

As also shown, the optical scanning system 500 further includes are-imaging lens 512 between the optical fiber and the first scanningmirror, and a collimator 514 between the first scanning mirror 506 andthe second scanning mirror 508. The re-imaging lens focuses the laserbeam emitted from the optical fiber 502 on or close to the firstscanning mirror's center of rotation 516, thereby re-imaging the fibertip at or close to the center of rotation. The first scanning mirrorreflects the laser beam as a divergent laser beam toward a collimatinglens. This lens collimates the divergent laser beam which issubsequently reflected by the second scanning mirror toward the scene.

In some examples, as shown, the first scanning mirror 506 is rotatablewith a faster angular velocity than the second scanning mirror 508 toscan the scene according to the scanning pattern. As also shown, thefirst scanning mirror may be rotatable along an azimuth axis (x-axis),and the second scanning mirror may be rotatable along an elevation axis(y-axis), to scan the scene according to the scanning pattern.

In some examples, the collimator 514 may be more generally locatedbetween the fast scanning mirror 506 and the scene 510. In examplesincluding the two scanning mirrors 506, 508 such as shown, this mayinclude the collimator located between them. In other examples, thecollimator may be located between the second scanning mirror 508 and thescene 510.

In some examples the collimator 514 may be replaced with a focus lensconfigured to focus the divergent laser beam from the scanning mirror toproduce a focused laser beam. The optical scanning system 500, then, maymore generally include an optic that is configured to collimate or focusthe divergent laser beam.

Many modifications and other implementations of the disclosure set forthherein will come to mind to one skilled in the art to which thedisclosure pertains having the benefit of the teachings presented in theforegoing description and the associated figures. Other suitableconfigurations of the optical scanning system are shown in FIGS. 6-10.In the optical scanning system shown in FIG. 5, the collimator islocated between the scanning mirrors, or between the first scanningmirror and the scene. In other example implementations, the collimatoris located still between the first scanning mirror and the scene, but itis also located between the second scanning mirror and the scene. Thisis shown in FIG. 6 for another optical scanning system 600 that maycorrespond to the optical scanning system 306 of the LIDAR system 300 ofFIG. 3, according to some example implementations.

As shown in FIGS. 7 and 8, in some example implementations, the opticalscanning system 700, 800 includes a focus mirror 714 in place of thecollimator 514, which may be located similar to the collimator in otherexample implementations. The optical scanning system of various exampleimplementations, then, may more generally include an optic that isconfigured to collimate or focus the divergent laser beam.

In other example implementations, the optical scanning system includesmore or less than the two scanning mirrors shown in FIGS. 5-8. In someof these example implementations, the optical scanning system includes ascanning mirror rotatable along multiple orthogonal axes to steer thelaser beam in multiple dimensions to scan the scene. These examples maysimilarly include an optic between the scanning mirror and the scene,such as a collimator or focus lens. Examples including amulti-dimensional scanning mirror are shown in FIGS. 9 and 10, whichillustrate optical scanning system 900, 1000.

In yet other example implementations, the optical scanning system maygenerate and detect multiple laser beams. In some of these examples, thelaser beam is multiple laser beams, and the optical fiber is an array ofoptical fibers coupled to the active optical circuit and configured toguide the multiple laser beams to fiber tips from which the multiplelaser beams are emitted. In these examples, the angle separation betweenthe laser beams may be a function of the focal length from the array tothe optic and fiber spacing. An example of an array 1102 and collimator1104 for multiple laser beams is shown in FIG. 11.

It is therefore to be understood that the disclosure is not to belimited to the specific implementations disclosed and that modificationsand other implementations are intended to be included within the scopeof the appended claims. Moreover, although the foregoing description andthe associated figures describe example implementations in the contextof certain example combinations of elements and/or functions, it shouldbe appreciated that different combinations of elements and/or functionsmay be provided by alternative implementations without departing fromthe scope of the appended claims. In this regard, for example, differentcombinations of elements and/or functions than those explicitlydescribed above are also contemplated as may be set forth in some of theappended claims. Although specific terms are employed herein, they areused in a generic and descriptive sense only and not for purposes oflimitation.

What is claimed is:
 1. A light detection and ranging (LIDAR) system comprising: an optical source to generate and transmit an optical beam; an optical fiber to guide the optical beam to a fiber tip from which the optical beam is emitted; a first scanning mirror rotatable along at least one axis to steer the optical beam to scan a scene, and collect light incident upon objects in the scene; a first lens, disposed between the optical fiber and the first scanning mirror, to focus the optical beam emitted from the optical fiber to converge at a location near a center of rotation of the first scanning mirror, the first scanning mirror to reflect the optical beam towards an optic; the optic, disposed between the first scanning mirror and the scene, to collimate or focus the optical beam reflected from the first scanning mirror; and a signal processor to determine a range of one or more of the objects from a return signal reflected from the one or more of the objects.
 2. The LIDAR system of claim 1, wherein the optical beam is reflected from the first scanning mirror as a divergent optical beam.
 3. The LIDAR system of claim 2, wherein the optic comprises a collimating lens to collimate the divergent optical beam from the first scanning mirror to produce a collimated laser beam that is directed toward the scene.
 4. The LIDAR system of claim 2, wherein the optic comprises a focus lens to focus the divergent optical beam from the first scanning mirror to produce a focused laser beam that is directed toward the scene.
 5. The LIDAR system of claim 2, wherein the optic comprises a focus mirror to collimate the divergent optical beam from the first scanning mirror to produce a collimated laser beam that is directed toward the scene.
 6. The LIDAR system of claim 1, wherein the first scanning mirror of the optical scanning system is rotatable along multiple orthogonal axes to steer the optical beam in multiple dimensions to scan the scene.
 7. The LIDAR system of claim 1, further comprising a second scanning mirror, wherein the optic is disposed between the first scanning mirror and the second scanning mirror.
 8. The LIDAR system of claim 7, wherein the second scanning mirror directs the optical beam toward the scene.
 9. The LIDAR system of claim 7, wherein the first scanning mirror and the second scanning mirror are rotatable along orthogonal axes to steer the optical beam in multiple dimensions to scan the scene, the first scanning mirror being rotatable with a faster angular velocity than the second scanning mirror to scan the scene.
 10. An optical scanning system comprising: an optical fiber to guide an optical beam to a fiber tip from which the optical beam is emitted; a scanning mirror rotatable along at least one axis to steer the optical beam to scan a scene; a first lens, disposed between the optical fiber and the scanning mirror, to focus the optical beam to converge near a center of rotation of the scanning mirror; and an optic disposed between the scanning mirror and the scene to collimate or focus the optical beam.
 11. The optical scanning system of claim 10, wherein the optical beam is reflected from the first scanning mirror as a divergent optical beam.
 12. The optical scanning system of claim 11, wherein the optic comprises a collimating lens to collimate the divergent optical beam from the first scanning mirror to produce a collimated laser beam that is directed toward the scene.
 13. The optical scanning system of claim 11, wherein the optic comprises a focus lens to focus the divergent optical beam from the first scanning mirror to produce a focused laser beam that is directed toward the scene.
 14. The optical scanning system of claim 11, wherein the optic comprises a focus mirror to collimate the divergent optical beam from the first scanning mirror to produce a collimated laser beam that is directed toward the scene.
 15. The optical scanning system of claim 11, wherein the first scanning mirror of the optical scanning system is rotatable along multiple orthogonal axes to steer the optical beam in multiple dimensions to scan the scene.
 16. The optical scanning system of claim 11, further comprising a second scanning mirror, wherein the optic is disposed between the first scanning mirror and the second scanning mirror.
 17. The optical scanning system of claim 16, wherein the second scanning mirror directs the optical beam toward the scene.
 18. The optical scanning system of claim 16, wherein the first scanning mirror and the second scanning mirror are rotatable along orthogonal axes to steer the optical beam in multiple dimensions to scan the scene, the first scanning mirror being rotatable with a faster angular velocity than the second scanning mirror to scan the scene.
 19. A method comprising: generating, by an optical source, an optical beam; directing the optical beam toward a first scanning mirror via an optical fiber; focusing, by a first lens, the optical beam near a center of rotation of the first scanning mirror; and collimating or focusing, by an optic, the optical beam as reflected from the first scanning mirror.
 20. The method of claim 19, further comprising: directing, by a second scanning mirror, the optical beam toward a scene to be scanned by the optical beam. 